Television process and apparatus



y 1938. A. J. CAWLEY v 2,118,160

v I TELEVISION PROCESS AND APPARATUS Original Filed June 5, 1930 2Sheets-Sheet l I 1 2/522 1/ INVENTOR "fli H10 May 24, 1938. A. J. CAWLEY2,118,160

- TELEVISION PROCESS AND APPARATUS Original Filejd June a, 19:0 2Sheets-Sheet 2 Patented May 24, 1938 UNITED STATES PATENT OFFICEOriginal application June a, 1930, Serial No. 459,368. Divided and thisapplication October 25, 1935, Serial No. 47,483

13 Claims.

The invention relates generally to the electransmission of opticalimages from one place to another bymeans of wire or wirelesscommunication. More particularly it is con-- ing about a much morebrilliant and detailed picture.

The light is plane polarized and then passed through an electromagneticor electrostatic rotating means and later through an analyzing means,the latter being so adjusted as to approximately extinguish the light.However, the operation is not limited to this action. The imagevariedtelevision current traversing the rotating means causes varying amountsof light to pass in accordance with the image being transmitted.

A special projection screen is described possessing a light polarizingsurface, as is also its method of manufacture. This polarizing surfacemay be substituted for the analyzing means.

A method of projecting with polarized light is also described whichutilizes both polarized components in such manner as to produce colored,daylight and stereoscopic projection.

An object is the resolving of a light beam from a light source into twobeams of plane polarized iight whose planes of polarization difier fromeach other by angles of 90, and the rotation of the planes ofpolarization of both of those beams by means of Kerr cells or theirequivalents in accordance with an image current, and the superscreen andemploying electromagnetic rotation of the plane of polarization therein.

Figure 1a illustrates a modification of the invention illustrated inFigure 1.

Figure? is a plan view of a method of projecting colored, daylight andstereoscopic pictures and also employing the principle of theelectromagnetic rotation of the planeof polarization of light.

Figure 3 is a plan view. of a method of producing television picturesutilizing the, rotation of the plane of polarization of light by causingitsreflection from the pole of an electromagnet which is traversed by animage-varied current.-

Figure 4 is a view of the polarizing screen and projecting means.

Fig. 4a shows a view oi the relation between the polarized light beamand the screen.

Figure 5 is a plan view of a television projection apparatus forproducing stereoscopic, colored images.

In Figure 1, a light source I is illustrated which may be an are light,incandescent fight or lamp, or glow lamp, but is here shown as a neonlamp, which as is well known, possesses the property of varying itsintensity many thousands of times per second, The lamp is shown asconnected in the usual manner in a television receiver, wires a and bcommunicating with the receiving, amplifying circuits. The light,however, may be an ordinary arc lamp la of Figure In, as used inprojectors, and may be lighted by an independent source of current, suchas the street mains. The optical system 2 acts to condense the lightinto a beam of parallel rays of light. This beam of light passes throughany desired form of means for plane polarizing light, and a Nikol prism,which is well known to those skilled in the art, is illustrated at 3.The light from source l is there fore, plane-polarized by prism 3 and insuch plane that it is more or less extinguished by the analyzer 6 whichit later in its course traverses. The light beam passes from prism 3through the cylinder 3, which may be made of any special form ofglass,such as silicated borate of lead, which is best adapted fordemonstration of the Faraday effect, which is the rotation of the planeof polarization. Or, 4 may be a transparent tube of any liquid, evenwater, or carbon bisulphide, or any gas such as oxygen which is suitablefor the demonstration of the Faraday effect. Surrounding tube 4 is asolenoid} which .istraversed-by the image-varied current, and whichcauses the solenoid to rotate the plane of polarization of the lightbeam to varying degrees. Optical elements I and la represent lenseswhich project the image upon the screen I, which may or may not beprovided with a polarizing surface as hereinafter described. Thelight-passes through the spiral line of openings in scanning disk 8,which is shown as being rotated in synchronism with a similar disc atthe sending station by motor 9. The mechanism of scanning an image bymeans of a disc having a spiral line of holes need not be described, asit is familiar to those skilled in the art of television. The light fromsource I is plane polarized by passing it through the polarizing means 3and setting the analyzer 6 to practically extinguish the light in thewell known manner. The image-fluctuated current passing through thesolenoid 5, causes the plane of polarization to be rotated to varyingdegrees causing more or less light to be passed by the analyzer 6,resulting in a variation in the intensity of the light. This variationis synchronous with the variation in light intensity of the image at thetransmitting station. This variation in light intensity combined withthe scanning produced by the disk 8 results in a reproduction of thetransmitted image upon the screen I 0.

If a neon lamp is used as the source I and if it is supplied with theimage-varied current, the

intensity of its light will be varied in accordance with the image beingtransmitted. We therefore, have two means of varying the light intensityacting in synchronism for the production of a television image, namely,the neon lamp and the electromagnetic rotation means for rotating theplane of polarization. A much more contrasted and detailed picture can,therefore, be produced than with the former alone, as now used inpractice.

The current is shown passing from the amplifying means of the receiverto wire a to lamp 1, to wire to transformer t and returning by wire b.The solenoid is placed in the secondary circuit of the transformer. Thetransformer may be omitted and the solenoid 5 connected directly to thereceiving circuit. The lamp l, particularly if an arc lamp, such as iaof'Figure 1a, may be illuminated by an entirely independent source oielectric current, as stated above, such as the street lighting mains. Ifthe current traversing the circuit a, b, c is pulsating direct current,then, due to the action of the transformer t, when the currentincreases, the current in the solenoid will pass in one direction, whileit will pass in the opposite direction when the current in circuit a, b,0, decreases. Current passing in one direction through the solenoid willrotate the plane of polarization in one direction, and will rotate it inthe opposite direction if the current changes its direction. This wouldgive a very sensitive apparatus. A direct current traversing thesolenoid 5 and never varying its direction,

but simply varying its intensity, will cause the rotation to take placein one direction only. The use of a neon lamp varying its intensity oflight in synchronism with the variations produced by the solenoid isvery desirable for home projection of television images.

In my application for Letters Patent, Serial No. 439,286, filed January2, 1921, for Daylight colored projection systems, I described a meansfor obtaining daylight pictures by means of polarized light and thisapplication describes means which are to coact with the apparatusdescribed therein. The screen may be an ordinary projection screen, orit may be a polarizing type of screen as described in the abovementioned application, as shown at the top of Figure-la. If a,

screen I0 is employed possessing a polarizing surface, it may be set ata certain position so as to extinguish the plane polarized, unrotatedlight beam, and analyzer 6 may be in that case, dispensed with. This isillustrated in Figure 4.

A polarizing screen as described in the above mentioned application maybe made by rubbing in the same direction the surface of a sheet of plateglass or other transparent medium with emery of a certain size ofparticles.

Figure 2 represents a projection system intended to utilize bothcomponents of the polarized light. Current passes from the usualtelevision receiving means to the lamp I, which may be of neon, by meansof wire a, and thence by wire 0 to solenoid 5b, by wire e to solenoid 5aand by wire b back to the receiver circuit. The optical system 2produces a parallel beam of light rays which impinges upon thepolarizing means 3a at the polarizing angle. This polarizing means 3a isshown as a bundle of thin glass plates, which as is well known,possesses the power of polarizing light. Approximately one half of thelight incident upon 3a is refracted and passes on to the glass cylinderll'b, while approximately the other half is reflected and passes on toglass cylinder 4a. The beam is thus resolved into two component beams,and each of the component beams is composed of plane polarized light.The planes of polarization of the two beams differ by an angle of 90, asis well known. The reflected beam passes through the glass or othercylinder 4a and thence to the totally reflecting prism II, which changesthe course of the beam and directs it upon the screen [0. The opticalelements I and la project the light upon a large area of the screen ii).The refracted beam passes through cylinder 4b, through analyzer 6,through total reflecting prism Ila, to optical elements I and lb andisprojected superposed upon the screen M. The analyzers 6 are to be usedto more or less extinguish the polarized beams both reflected andrefracted, if the screen has no polarizing surface. The reflected beamis scanned by scanning disc 8a and the refracted beam isscanned by thedisc 9b. They may be scanned in absolute synchronism. However, in thedrawings, they are shown as scanning lines alternately in the two beams,as indicated by the fact that a scanning hole h of disk 8a is shownscanning the reflected beam, while no scanning hole is shown in disk 9bin the refracted beam. In the next instant, a scanning hole in disk 9bwill scan the refracted beam, while none scans the reflected beam. Insuch case, a color screen 622, such as orange-red may be placed in thepath of the reflected beam and a blue-violet screen 67", in the path ofthe refracted beam, and colored pictures projected, as two distincttransmissions are possible. If suitable ridges such as r are provided(and if a similar arrangement is given to the lenses taking the pictureat the transmitting station) it will be seen that the reflected beamilluminates but one face of each of the ridges, while the refracted beamilluminates but the other of each ridge. This will give a method ofproducing stereoscopic pictures, which together with the use of colorscreens may be both stereoscopic and colored. They may also possess adaylight property. However, if a polarizing surface is given to screenID, as indicated at the top of Figure 1a, daylight pictures will beobtained, through the action of the polarized light in accordance withthe method described in the above application.

In the operation of the system, if the screen l0 has no polarizingsurface, the image-varied current traversing the electromagneticrotators 5a and 5b cause a rotation of the plane of polarization of boththe reflected and the refracted beams of light. The refracted beam,before it reaches 4b, is polarized in a plane vertical to that Itinguish the light of its particular beam. Solenoids 5a and 5b are soplaced and connected that they rotate the planes of polarization of thetwo beams to overcome the extinguishment produced by analyzers 6. Theanalyzers 6 may be Nikol prisms, plates of quartz, or any other meansused heretofore as an analyzer. In this apparatus, an are lamp may beused if desired, or any other source of illumination desired. The discs,as before mentioned, may be operated to scan in synchronism oralternately, as desired. The wiring of the apparatus is not limited tothat shown, as many other circuit arrangements may be used.

If the screen I is provided with a polarizing surface, it should be setso that it will reflect light polarized midway between the two planes ofpolarization of the reflected and refracted beams of light. This isillustrated in Figure 4, where the polarizing surface lop is shownmidway between the planes of polarization :1: and y of the two lightbeams passing through the lenses Ia and lb, also illustrated in Figure2. The dotted lines indicate the position to which the planes ofpolarization of the beams are rotated to correspond with that of thepolarizing ridges Hip.

Figure 3 is another modification of the main invention, which is themagnetic rotation of the plane of polarization. Here, however, thepolarized light is rotated by reflection from the polished pole of anelectromagnet. The light passes through the polarizer, which is hereshown as a Nikol prism 3. It is reflected from the surface of the magnetM. This electromagnet is provided with an image-varied televisioncurrent in the well known manner. The analyzer is set to extinguish thepolarized light when the current traversing the magnet M corresponds toa shaded portion of the image. The analyzer is shown at 6. As thecurrent increases in value, the plane of polarization is rotated beyondthe extinguishing position to a degree depending upon the intensity ofthe current, and light traverses the,

analyzer 8 correspondingly. The optical element 'Ie projects light uponthe screen ID. The scanning disc 8 scans the image'field in the usualmanner.

Figure 5 illustrates an apparatus also adapted to the stereoscopicprojection of television images. Light from lamp i, which is hererepresented as being a crater neon lamp, but which may 'be an arc lampor another light source, is formed into a parallel beam by means of lens2. A crater neon lamp or'other point source of light readily lendsitself to the production of a parallel beam of light. This beam impingesupon the polarizer, which is here shown as a bundle of sheets of thinplate glass 3a, which is very inexpensive. The beam of light, accordingto well known principles, is resolved into two component beams of planepolarized light whose planes of polarization differ by an angle of 90.Each of those component beams pass through a Kerr cell or a Karolus cell5K and 5C. The analyzers 6 and 6a are so set as to just extinguish thelight beams when no current is traversing the cells. As the amplifiedtelevision current traverses the cells 5K and 50, the planes ofpolarization of the respective beams are rotated more or less in ac- Thetwo analyzers G are set difierently in order that each might. ex-

cordance with the variation in intensity of the television current, andmore or less of the light is permitted to pass by the analyzer inaccordance with the rotation of the planes beyond the point ofextinguishment.

The amplified television current comes in over the wires 1 and m and issent through the wires 1) to cell 5K and wire e to cell 50, to wire 10,to switch k and to wire m. In such case, the light source I consists ofan independent source of illumination, such as an are light connected tothe street mains. However, a crater neon lamp may be used as l, inwhich'case the switch n is closed and then the image current passesthrough the neon lamp directly and is shunted around the two cells whichmay be placed in series or in parallel in this shunt. It is to be notedthat the neon lamp depends upon amperage forits operation while theaction of the Kerr cell is mostly electrostatic, i. e., it dependsparticularly upon efiect; constitutes a very desirable cooperation ofelements that is decidedly novel. One does not rob the other of anydesirable form of energy.

The two beams of light after traversing the Kerr. cells and analyzersencounter the prisms Ii and Ha, and the latter act to reflect the beamsupon the screen III, which is here shown as provided with round ridges1'. Thus the two images formed by the beams are projected insuperposition upon-.the screen II]. It is to be noted that the elements5K, 6a and I I should be shown much closer together, while the distanceof the screen ill from the rest of the apparatus should be much greaterthan that shown. This combination possesses the very great advantagethat all of the available light is used and that one component is notwasted, as is done in ordinary television apparatus in which polarizedlight is used. A similar the right andleft eyes are obtained. The righteye image is projected upon the right sides of the ridges r and the lefteye images are projected upon the left sides of the ridges 1'alternately. If the screen it! and ridges r are made transparent, astereoscopic image may be seen on the opposite side of the screen, also.

Suitable colored screens may be interposed in the beams at thetransmitting and receiving stations and color effects may be thus addedto the stereoscopic effects. 'Ihus colored stereoscopic images may beproduced that will consist of approximately twice the amount of lightthat is used in any television system using polarized light valves, suchas the Kerr or the Karolus valves. If a crater neon lamp is used as thesource I, twice the definition'obtainable otherwise is secured, as itmay also have its intensity varied-in accordance with the current. Thoseare very great advantages. It is to be noted that the ridges serve togive a certain degree of daylight effect.

This application is a continuation-in-part of my application Serial No.459,368 oi. June 3, 1930 for Televislo nprocess and acontinuation-in-part of application Serial No. 627,176, filed July 30,1932, for Stereoscopic projection apparatus.

Having described my invention, 1 claim as new and desire to secure byLetters Patent:

1. In combination: a light soure means for producing a beam of parallelrays from said light source, polarizing means for converting said beaminto two beams of plane polarized light having their light polarizingplanes at different angles and said beams having different directions,means for extinguishing the said beams at certain po@ sitions of theirpolarizing planes, electromagnetic means coacting with each of saidbeams to rotate their planes to various positions beyond the points ofextinguishment when traversed by an imagevaried current, a screen, meansfor superposedly projecting said beams upon said screen, means (orconsecutively permitting the passage of said light to consecutive areasof said screen to reproduce a television image.

2. The process of producing colored television imageswhich consists insuperposedly projecting two component beams of light upon a definiteplane from a single light source, limiting the light of each of saidbeams to a definite elementary color, alternately scanning said beamsand simultaneously varying the intensity of said light source and ofsaid light constituting said beams.

3. In combination: a light source, means for producing a beam ofparallel rays from said light source, polarizing means converting saidbeam into two beams of plane polarized light having their lightpolarization planes at different angles and said beams having differentdirections, a projection screen provided with analyzing means,electromagnetic means coacting with each of said beams to rotate theirplanes to various positions beyond the points of extinguishment whentraversed by an image-varied current, means for consecutively permittingthe passage of said light to consecutive areas of said screen to producea composite image.

4. A television apparatus consisting of a light source, means forproducing a beam of parallel rays from said light source, polarizingmeans converting the light of said beam into two beams of planepolarized light having their planes of polarization at different anglesand said beams having different directions, means for extinguishing thelight, of each of said beams at certain positions 01! their polarizingplanes, a color filter in the path of each of said beams,electromagnetic means coacting with each of said beams to rotate theirplanes to various positions beyond the points oi extinguishment whentraversed by an imagevaried current, a screen, means for superposedlyprojecting said beams upon said screen and means for consecutivelypermitting the passage of said light to consecutive areas of said screento produce a colored television image.

5. A television apparatus consisting of an image-varied light source,means for producing a beam of parallel rays from said light source, a

polarizing means converting said beam into two beams of plane polarizedlight having their planes of polarization at diflerent angles and saidbeams having diilerent directions, means for extinguishing the light ofsaid beams at certain positions of their polarizing planes,electromagnetic means coacting with each of said beams to rotate theirplanes to various positions beyond the points oi extinguishment whentraversed by an imagevaried current, a screen, means for superposedlyprojecting said beams upon said screen, means for consecutivelypermitting the passage of said light to consecutive areas of said screento reproduce a television image.

6. A stereoscopic television apparatus consisting of a light source,means for producing a beam of parallel rays from said light source,polarizing means converting said beam into two beams of plane polarizedlight having diflerent directions and having their planes ofpolarization at different angles, means for extinguishing said beams atcertain positions of their polarizing planes, electromagnetic meanscoacting with each oi! said beams to rotate their planes to variouspositions beyond the points of extinguishment when traversed by animage-varied current, a projection screen, a ridged surface on saidscreen, means for projecting each of said beams upon each side 01 saidridges, means for consecutively permitting the passage of said light toconsecutive areas of said screen.

'7. In a modulated polarized light system, means for increasing thelight efllciency thereof, comprising a source of light, a polarizer inwhich the light from said source is polarized in a reflected beam, and atransmitted beam, means for modulating said beams, and means forrecombining the polarized beams.

8. In a modulated polarized light system, means for increasing the lighteiiiciency thereof, comprising a source of light, a polarizer in whichthe light from said source is polarized in a reflected beam, and atransmitted beam, magnetic means responsive to varying signals forseparately rotating said beams, and means for recombining the polarizedbeams.

9. In a modulated polarized light system, means for increasing the lightefilciency thereof, comprising a source of light, a polarizer in whichthe light from said source is polarized in a reflected beam, and atransmitted beam, magnetic means responsive to varying signals forseparately rotating said beams, and means for recombining the polarizedbeams, and magnetic means comprising coils responsive to said varyingsignals, and poles therefore having reflecting means from which thepolarized beams are reflected.

10. The process of producing television images consisting of forming abeam of plane polarized light from a light source, applying an imagevaried current to said light source, and simultaneously causing saidcurrent to rotate the plane of polarization of said beam to varyingdegrees and successively exploring the successive elemental areas ofsaid light beam in order to produce an image by synchronously varyingthe in-- tensity of said source and rotating the plane of polarizationof said light beam.

11. In combination: a variable intensity light source traversed by animage varied current, means for producing a parallel beam of planepolarized light from said light source, an analyzer acting to extinguishsaid beam at a certain position, a light valve also traversed by saidimage varied current and acting to rotate the plane of polarization ofsaid beam to various degrees and means for successively exploring thesuccessive elemental areas of said light to produce a television imageby the synchronous variation of the intensity of said light source andthe rotation of said plane.

12. In combination: a variable intensity light source traversed by animage varied current, means for producing a parallel beam of planepolarized light from said light source, an analyzer acting to extinguishsaid beam at a certain position, a light valve also traversed by saidimage varied current and acting to rotate the plane of polarization ofsaid beam to various degrees, means for projecting the light of saidbeam upon a screen and means for successively exploring the elementalareas of said projected light to produce a television image by thesynchronous variation of the intensity of said light source and therotation of said plane.

13. In combination: a variable intensity light source traversed by animage varied current, means for producing a parallel beam of planepolarized light from said light source, means for projecting the lightof said beam upon a projecting screen, a polarizing screen provided witha polarizing surface and acting to extinguish said light at certainpositions of its plane of polarization, a light valve traversed by saidimage varied current and acting to rotate said plane of polarization tovarious degrees in accordance with said current and means forsuccessively exploring the elemental areas of said projected light toproduce a television image by the synchronous variation of the intensityof the light of said source and the rotation of said plane.

ALOYSIUS J. CAWLEY.

